Sprout and anchovy gratin with porcini crumb

Method

1. Trim the sprouts, halve and set aside, reserving the trimmings for the gravy, if making.
2. Put the goose fat in a large sauté or frying pan over a medium heat. Once melted, add the anchovies and half their oil (reserve the rest) and stir until dissolved. Stir in the shallots, cook for 3 minutes, then add the garlic and bay leaves and cook for another minute.
3. Add the sprouts to the pan and cook for 4 minutes until they’ve turned bright green. Add the pickled walnuts and their vinegar, season with a pinch of salt and pepper, cook for another minute, then scrape into an ovenproof dish.
4. Return the pan to the heat and add the wine. Bubble for about 8 minutes until reduced by half, then stir in the cream. Bring to the boil, then pour the cream mixture over the sprouts. Stir together and leave to cool. If making ahead, the dish can then be covered and kept in the fridge for up to 24 hours.
5. For the porcini crumb, put the mushrooms in a heatproof bowl and cover with 200ml just-boiled water. Leave to soak for 10 minutes, then strain the liquid into a container and reserve for the gravy, if making. Finely chop the mushrooms.
6. Put the remaining anchovy oil in a large frying pan over a medium heat. Add the mushrooms and breadcrumbs, season with a pinch of salt and pepper, then cook for about 4 minutes, stirring regularly, until golden. Add the thyme leaves. If making ahead, set aside to cool, then transfer to an airtight container and store at a cool room temperature for up to 24 hours.
7. When ready to cook the gratin, heat the oven to 200°C fan/gas 7. If prepared ahead, take the sprout mixture out of the fridge 20 minutes before cooking to bring it up to temperature. Spread the crumbs over the sprouts, then bake for 15-20 minutes until golden, crisp and bubbling.